Secondary cataract inhibitor

ABSTRACT

The present invention relates to a secondary cataract inhibitor comprising as the active ingredient N-(3,4-dimethoxy-cinnamoyl)anthranilic acid represented by the formula:                    
     or a pharmaceutically acceptable salt thereof, which has an inhibitory activity on posterior capsule opacification formation after cataract surgery and is useful for the prevention or treatment of secondary cataract.

FIELD OF THE INVENTION

The present invention relates to a pharmaceutical composition beinguseful as a secondary cataract inhibitor.

More particularly, the present invention relates to an inhibitor forsecondary cataract after cataract surgery, which inhibitor comprises asthe active ingredient N-(3,4-dimethoxycinnamoyl)-anthranilic acidrepresented by the formula:

or a pharmaceutically acceptable salt thereof.

BACKGROUND OF THE INVENTION

Cataract is a refractory ocular disease which occurs and develops due tovarious factors. The discase subsequently leads to lower vision due tolens opacity. Most of this ocular discase is age-related senilecataract. The incidence of cataract is thought to be 60-70% in personsin their sixties and nearly 100% in persons eighty years old and more.In proceeding toward a society composed largely of elderly people, theprevention and treatment of cataract will become more important for thefuture. However, at the present time, there is no sure therapeutic agentwhich has an inhibitory activity on the development of cataract.Therefore, the development of an effective therapeutic agent has beendesired. Presently, the treatment of cataract depends upon thecorrection of vision using eye glasses, contact lenses etc. or surgicaloperations such as insertion of an intraocular lens into the capsulalentis after extracapsular cataract extraction.

In cataract surgery, the incidence secondary cataract after surgery isbeen a problem. Secondary cataract is equated with opacity present onthe surface of the remaining posterior capsule following extracapsularcataract extraction. The mechanism of secondary cataract is mainly asfollows. After excising lens epithelial cells (anterior capsule),secondary cataract results from migration and proliferation of residuallens epithelial cells, which are not completely removed at the time ofextraction of the lens cortex, onto the posterior capsule leading toposterior capsule opacification. Also, secondary cataract results fromabnormal proliferation of the residual lens epithelial cells in theequator followed by formation of Elschnig pearls.

In cataract surgery, it is impossible to remove lens epithelial cellscompletely, and consequently it is difficult to always prevent secondarycataract. It is said that the incidence of the above posterior capsuleopacification is 40-50% in aphakic eyes and 7-20% in pseudophakic eyes.

On the other hand, in the field of cataract medication, extensive studyhas been actively promoted in order to find substances capable ofinhibiting secondary cataract. Up to now for example, it has been wasconfirmed that metabolic antagonists such as mitomycin, daunomysin, 5-FUand colchicine are effective secondary cataract inhibitors. However,concerns about these drugs have been raised in view of problems such asserious side effects which have been found [Atarashii Ganka, Vol. 12,No. 3, pp 451-452 (1995); Japanese Journal of Ophthalmic Surgery, Vol.8, No. 3, pp. 439-446 (1995)] and accordingly, these drugs have not beenused to use clinically. It has also been reported that the formation ofsecondary cataract was significantly inhibited when an insertedintraocular lens was coated with indometacin. Furtherethylenediaminetetraacetic acid (EDTA) has been found effective ininhibiting secondary cataract [Japanese Journal of Ophthalmic Surgery,Vol. 8, No. 3, pp. 439-446 (1995); IOL & RS, Vol. 19, No. 2, pp. 78-82(1995); Japanese Patent Application Publication (kokai) No.Hei.8-175984]. However, clinically satisfactory drugs for preventing andinhibiting secondary cataract have not yet been developed.

N-(3,4-dimethoxycinnamoyl)anthranilic acid (generic name: Tranilast)represented by the above formula (I) of the present invention has beenwidely used in medicines for the treatment of allergic disorders such asbronchial asthma, allergic rhinitis, atopic dermatitis and allergicconjunctivitis, as well as cutaneous disorders such as keloid andhypertrophic scar. For example, it has been known that Tranilast hasinhibitory activities on chemical mediator release caused by an allergicreaction, excessive collagen accumulation by fibroblast cells incutaneous tissues and excessive proliferation of smooth muscle cells incoronary artery vessels.

However, it has not been previously disclosed that Tranilast has aninhibitory activity on secondary cataract formation and it until now hasnot been known that Tranilast is can be useful as an inhibitor forsecondary cataract.

SUMMARY OF THE INVENTION

The present invention relates to a secondary cataract inhibitor whichcomprises as the active ingredient N-(3,4-dimethoxycinnamoyl)anthranilicacid represented by the formula:

or a pharmaceutically acceptable salt thereof.

The present invention also relates to a method for the prevention ortreatment of secondary cataract which comprises administeringN-(3,4-dimethoxycinnamoyl)anthranilic acid represented by the aboveformula (I) or a pharmaceutically acceptable salt thereof.

The present invention also relates to use ofN-(3,4-dimethoxycinnamoyl)anthranilic acid represented by the aboveformula (I) or a pharmaceutically acceptable salt thereof for themanufacture of a pharmaceutical composition for the prevention ortreatment of secondary cataract.

Furthermore, the present invention relates to use ofN-(3,4-dimethoxycinnamoyl)anthranilic acid represented by the aboveformula (I) or a pharmaceutically acceptable salt thereof as a secondarycataract inhibitor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating an inhibitory activity on rat lensepithelial cell proliferation by Tranilast. The axis of the ordinatesshows number of rat lens epithelial cells (x10⁴ cells), and the axis ofthe abscissas shows Tranilast concentrations to be added (μg/ml). Thesymbols * and ** in the graph show the significantly difference atp<0.05 and p<0.01, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have extensively studied in order to findcompounds having an inhibitory activity on secondary cataract formation.As a result, it was found that N-(3,4-dimethoxy-cinnamoyl) anthranilicacid represented by the above formula (I) of the present invention has amarked inhibitory effect on lens epithelial cell proliferation and isextremely useful as a secondary cataract inhibitor, thereby forming thebasis of the present invention.

The present inventors have shown that Tranilast significantly suppressproliferation of lens epithelial cells in in vitro testing using ratlens epithelial cells.

Accordingly, it is believed that Tranilast has an excellent inhibitoryeffect on lens epithelial cell proliferation and consequently is anextremely useful compound as a secondary cataract inhibitor.

Therefore, pharmaceutical compositions which are useful as secondarycataract inhibitors comprise as the active ingredient Tranilast or apharmaceutically acceptable salt thereof.

Various methods for the preparation of Tranilast and salts thereof whichare active ingredients are known and these compounds can be readilyprepared according to methods described in literature and the like(Japanese Patent Application Publication (kokoku) No.Sho.56-40710; ibid.No.Sho.57-36905; ibid. No.Sho 58-17186; ibid. No.Sho.58-48545; ibid.No.Sho.58-55138; ibid. No.Sho.58-55139; ibid. No.Hei.01-28013; ibid.No.Hei.01-50219; ibid. No.Hei.03-37539 etc.).

As examples of pharmaceutically acceptable salts of Tranilast, saltswith inorganic bases such as a sodium salt and a potassium salt, saltsformed with organic amines such as morpholine, piperazine andpyrrolidine and salts formed with amino acids can be illustrated.

When the pharmaceutical compositions of the present invention areemployed as a practical treatment, various dosage forms of thepharmaceutical compositions can be used depending. Preferably, eyedrops,injections, eye ointments or methods such as in plantation afterincorporating composition into pellet or microcapsule form and insertionafter pre-coating the intraocular lens can be illustrated.

These pharmaceutical compositions can be formulated by admixing,diluting or dissolving Tranilast, optionally, with appropriatepharmaceutical additives such as excipients, disintegrators, binders,lubricants, diluents, buffers, isotonicities, antiseptics, moisteningagents, emulsifiers, dispersing agents, stabilizing agents anddissolving aids in accordance with conventional methods and formulatingin a conventional manner depending upon the dosage form.

For example, eyedrops can be formulated by dissolving Tranilast or apharmaceutically acceptable salt together with a basic substance withheating in sterilized water in which a surface active agent isdissolved, adding polyvinylpyrrolidone, optionally adding appropriatepharmaceutical additives such as a preservative, a stabilizing agent, abuffer, an isotonicity, an antioxidant and a viscosity improver, anddissolving completely.

Injections can be directly injected into diseased tissues such ascornea, crystalline lens and vitreous or their adjacent tissues by usinga fine needle, and can be also used as intraocular perfusate.

The pharmaceutical compositions of the present invention can beadministered as sustained release preparations. For example, Tranilastor a salt thereof can be incorporated into a pellet or microcapsule of asustained release polymer as a carrier, and the pellet or microcapsulesurgically in planted into the tissues to be treated. Also, Tranilast ora salt thereof can be applied by inserting an intraocular lenspre-planted with the Tranilast composition. As examples of sustainedrelease polymers, ethylene-vinylacatate copolymer,polyhydromethacrylate, polyacrylamide, polyvinylpirrolidone,methylcellulose, lactic acid polymer, lactic acid-glycolic acidcopolymer and the like can be illustrated. Preferably, a biodegradablepolymer such as lactic acid polymer and lactic acid-glycolic acidcopolymer can be illustrated.

When the pharmaceutical compositions of the present invention areemployed as a practical treatment, the dosage of Tranilast or apharmaceutically acceptable salt thereof as the active ingredient isappropriately decided depending on the body weight, age, sex, degree ofsymptoms of each patient to be treated. For example, when instilling toeyes, these compounds can be administered approximately within the rangeof from 10 μg to 50 mg per day per adult human.

The dose of Tranilast or a pharmaceutically acceptable salt thereof canbe appropriately increased or decreased depending on the degree ofsymptoms present and therapeutic value of such dosage on each patient tobe treated.

The present invention is further illustrated in more detail by way ofthe following Examples.

EXAMPLE

Inhibitory Activity on Lens Epithelial Cell Proliferation

{circle around (1)} Culture of Rat Lens Epithelial Cells

Rat crystalline lens was harvested and cut into narrow strips. Thestrips were adhered to a culture plate and subcultured in Dulbecco'smodified Eagle's Medium (DMEM) containing 10% fetal calf serum (FBS) at37° C. in an atmosphere of 5% CO₂ in air for 4 days. On day 4 (at thepoint that lens epithelial cells had migrated and profilated fromcrystalline lens tissues), the medium was aspirated and cells weregently washed with phosphate-buffered saline (PBS(−)). Then, the PBS(−)was aspirated, an aliquot of 0.25% trypsin solution containing 0.02%EDTA was added to the culture plate, and the morphology of the cells wasobserved under phase-contrast microscopy. When cells were going to beround, an equal value of DMEM containing 10% FBS was added to thetrypsin solution to stop the action of trypsin. Attached cells wereharvested from the plate by pipetting the medium using a slender pasturepipette. The cell suspension was transferred into spit, then medium wasadded to the spit, and the cell suspension was mixed about 20 timesvigorously by pipetting with a pasture pipette and centrifuged at100-110×g for 1 minute. After the supernatant was discarded, freshmedium was added to the precipitate, and the lens epithelial cellsuspension was prepared by pipetting using a pasture pipette. Thesuspension was further subcultured in DMEM containing 10% FBS to use forexperiments.

{circle around (2)} Preparation of Test Drugs

Tranilast was added to a 1% aqueous sodium bicarbonate solution toprepare a 1.0% solution and dissolved by warming at 70° C. The solutionwas sterilized with a millipore filter and diluted with DMEM containing10% FBS to a final prescribed concentration.

{circle around (3)} Experimental Method

Cell suspension (2×10⁴ cells/0.1 ml) and DMEM medium (1.9 ml) containingvarious concentration of Tranilast and 10% FBS were added to a cultureplate (60 mm), and cultured at 37° C. in an atmosphere of 5% CO₂ in air.After 4 days, the medium was aspirated, the cells were washed withPBS(−), and 1 ml of 0.25 % trypsin solution containing 0.02% EDTA wasadded to the plate. After harvesting cells from the plate by pipettingusing a pasture pipette, the number of viable cells was counted using ahemocytometer.

{circle around (4)} Assessment of Effect

Mean and standard variation values of each group were calculated.Statistical analysis of significance was performed by a one-way analysisof variance and statistical significance was confirmed. Thereafter,analysis of significance between groups was performed by Dunnett'smultiple test.

{circle around (5)} Results

As shown in FIG. 1, Tranilast significantly suppressed the proliferationof lens epithelial cells in a concentration-dependent manner.

Industrial Applicability

A pharmaceutical composition comprising as the active ingredientTranilast or a pharmaceutically acceptable salt thereof has markedinhibitory activity on lens epithelial cell proliferation and issuitable as a secondary cataract inhibitor.

What is claimed is:
 1. A method for the prevention or treatment ofsecondary cataract which comprises administering subsequent to cataractsurgery N-(3,4-dimethoxycinnamoyl)anthranilic acid represented by theformula:

or a pharmaceutically acceptable salt thereof.
 2. The method of claim 1,wherein said N-(3,4 dimethoxycinnamoyl)anthranilic acid orpharmaceutically acceptable salt thereof is administered in the form ofeyedrops.
 3. The method of claim 1, wherein said N-(3,4dimethoxycinnamoyl)anthranilic acid or pharmaceutically acceptable saltthereof is administered in the form of an eye ointment.
 4. The method ofclaim 1, wherein said N-(3,4 dimethoxycinnamoyl)anthranilic acid orpharmaceutically acceptable salt thereof is implanted into oculartissue.
 5. The method of claim 4, wherein said N-(3,4dimethoxycinnamoyl)anthranilic acid or pharmaceutically acceptable saltthereof is formed into a pellet or microcapsule comprising a sustainedrelease polymer as a carrier for said N-(3,4dimethoxycinnamoyl)anthranilic acid.
 6. The method of claim 5, whereinsaid sustained release polymer is a lactic acid polymer or a lacticacid-glycolic acid copolymer.
 7. The method of claim 2, wherein saidN-(3,4 dimethoxycinnamoyl)anthranilic acid or pharmaceuticallyacceptable salt thereof is administered subsequent to extra-capsularcataract extraction.